Research Objectives To determine the effects of continuous, therapeutic ultrasound, as used in physical therapy; or injected murine tumors. Project Summary Ultrasound, at frequencies 1 and 3 MHz and intensities of 5 through 2.0 w/cm2, is used by physical therapist for therapeutic purposes. This therapeutic ultrasound increases the tissue temperature in the area under the transducer by 1-5 degreesC. A cancer diagnosis is believed to be a contraindication to the use of therapeutic ultrasound because of the possibility of ultrasonically induced acceleration of tumor growth. However, recent studies have shown that ultrasound at high tissue temperatures, 5-40 degreesC higher than those used in physical therapy, can decrease the size of malignant tumors. This study was designed to test whether therapeutic ultrasound at low tissue temperatures would increase the growth and metastasis of tumors in mice. 71 female C57 black 6 mice injected with subcutaneous MCA 205 (sarcoma) tumors received 10 treatments of ultrasound over a two week period or two weeks of no treatment. Tumors were measured pre- and post excision and mice were sacrificed then dissected to determine metastasis. This project is completed.